If you click Start, you should be able to click Control Panel. In there, there should be a globe icon with the name Regional & Language Settings; DoubleClicking that should bring you to the Regional Options which has a dropdown list where you can pick English; you can always pick to restore whatever you have now.

but i think my problem is my lang ! for example i see my this folder (en_GB) in the c:\doncumet and setting\adobe\....

but it must be (en_US) .!!!!!!!!!!!!

even time i reinstalled adobe lllustrator my lang steup that installed (en_GB) ...........but i think it must be (en_US) becuse in Other my Computer in the home this folder name is (en_Us) .....!!!!!!!!!!!!!!!!!

Well you said it worked good before.. if lang is the prob. then it shouldnt have worked at all... i am no expert.. i shall try to help on basis of my experience... i was once in the same situation but it was adobe reader instead... i had a hard time looking for the sulution but finally i am now running reader 8 (one version below). But a few things might help. Does it give any error like runtime error or something or it simply just 'goes off'? Did you updated your OS or antivirus recently maybe a new windows service pack or a new antivirus which would block the startup process... did you try to restore your windows to the time and settings when it worked correctly??

The initial information, that the issue arose suddenly, at startup of the PC, seemed to indicate corruption of the preferences, which are saved during closedown of Illy, probably owing to a Windows error.

When it comes to changing things in Windows, I am not. The overly detailed account in post #6 was merely a reflexion of my own uncertainty concerning Windows, and other MS applications, apart from Worst which is just that.

Two weeks ago I needed to change the extension of files from JSX to JS to get the JET scripts to work, http://forums.adobe.com/message/2415618#2415618. It took me quite a while to get the extensions displayed so they could be renamed, in XP. And now I cannot even remember how I did it.

I believe the strangenesses of different applications may appear more or less strange, depending on how they fit your own.

In some cases, the crash happens during a certain initiation state, and the window showing it may give a clue. When it happens at once, it is something more fundamental.

Have you tried creating a new user and tried to start Illy from that?

It might also be a disturbance from an anti virus application, not just from a firewall (Norton seems to be especially troublesome), so maybe a a disconnexion from the internet followed by a closedown of any security software might be worth trying.

Obviously, there must be a certain error or corruption causing the issue, but I still have no new suggestions.

If your (main) harddisk is from Seagate and/or Maxtor, you may use Maxtor Maxblast 5 to create a full image of it and save on another disk (harddisk or DVD, if the latter is sufficient). This may apply to before and after, if you have to restore the PC completely. In any case, it may be your friend, to use when thing are right, before they go wrong.

Surely he, not to mention all the others, must be hanging around some other building... ???? Any idea which or where?

Len stopped as a host about two years ago, I think; he needed to do more about his business. He has only posted a few times since then, in the first months. Sadly, many friends from the days of the fair forums show up rarely or not at all.

Can't say much about the topic at hand since I'm not on W7, but empty screens = overlay drawing issues. That's true for any OS. In turn that would lead to the conclusion, that you need to fix your graphics card river more than anything else. That's probably what happened, anyway - some Windows Update replaced a DirectX DLL or installed a new graphics driver without asking. I suggest you do the following:

Windows should now come up with a message about newly found hardware and set the default graphics driver. This will either be the generic WXGA driver or an older version of a branded driver from intel, NVidia or ATI. in any case, it might fix things. Then restart and boot into Windows normally. from there, check your graphics settings. Install a proper new driver only if you really need it.

Moving the prefs folder has already been advised, but there is no shame in trying again. Move/ delete C:\Users\Mohsen\AppData\Roaming\Adobe\Adobe Illustrator CS4 Settings\en_US and see if it helps in any way. What is particulalrly suspicious is the document templates not showing up in the welcome dialog, so you may also have a permission problem somewhere, but that's hard to tell from your limited info...

Does it mean that if you move that font out (of the Fonts folder), the issue goes away?

If so, it means that your assumption in post #4 was right (that it was issue 1. in post #3), and you have your solution: it also means that you will have to do without that font or find a viable replacement.

Illy is more particular than most other applications when it comes to the quality of fonts.